The bit manipulation insturctions (BTFxx, BSF and BCF) all include the bit
number as an immediate value within the instruction. You cannot pass a bit
number to these instructions in  a register.

However, you can get the same effect by using a bit _mask_ rather than a bit
_number_ and using the ANDWF or IORWF instructions. You can convert a bit
number to a bit mask using a short table lookup function.

Bob Ammerman
RAm Systems
(high performance, high function, low-level software)

----- Original Message -----
From: Russell Farnhill <r.farnhill@STOR-WAVE.CO.UK>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, June 26, 2000 6:17 AM
Subject: [PIC]: asm question


> Hi all,
>
> I have just started learning asm and playing around with a 16f84. I've
> already read
> a couple of tutorials from the net and now have a question. How do I
create
> a function
> that uses a bit orientated command and pass its arguments via a register.
I
> have
> included a small piece of code to try and illustrate.
>
> #include        "p16f84.inc"
> #DEFINE PAGE0 bcf STATUS,5
> #DEFINE PAGE1 bsf STATUS,5
>
> RBpin equ 0x0C          ; Port B pin number
>
>
>         org 4
>         goto start
>
> start
>         clrf    PORTB           ; clear portb
>         PAGE1                   ; select bank 1
>         clrf    PORTB           ; portb all output's
>         PAGE0                   ; select bank 0
>
> loop    movlw   0               ; bit 0 portb
>         movwf   RBpin           ; move bit select into register
>         call    foobar  ; test function
>         goto loop
>
> foobar
>
>         bsf     PORTB,RBpin
>         return
>
>         END
>
> When I compile this I get the error "Argument out of range.  Least
> significant bits used".
> I guess this is because bsf expects a single bit arg but I pass it a byte.
I
> tried loading
> W with my bit number and then read W from within my function which worked
> fine, but if I
> need to pass 2 args I can't use W as one arg overwrites the other.
>
> Any suggestions ?
>
> Thanks Russell.